federalism vs tetrarchy

federalism

noun
  • A system of national government in which power is divided between a central authority and a number of regions with delimited self-governing authority. 

  • Covenantalism. 

  • The belief that such a system is superior to other forms of government. 

tetrarchy

noun
  • The land ruled by such a government, either together or separately. 

  • A government where power is shared by four people, especially (historical) the Herodian tetrarchy established in Judea after the death of Herod and the Tetrarchy of Diocletian which ruled the Roman Empire in the years 293-313. 

How often have the words federalism and tetrarchy occurred in a corpus of books? (source: Google Ngram Viewer )